Method of impregnating wood



Sept. 3, 1935. c. SCHMITTUTZ METHOD OF IMPREGNATING WOOD Filed Sept. 28,1954 I I INVENTOR. gar/ 56/)(174072 A ORNEY.

J55 the Patented Sept. 3, 1935 UNITED STATES PATENT oFFicE METHOD OFIMPREGNATING WOOD Carl Schmittutz,

Bad Kissingen, Germany, as-

signor to Osmose Holzimpraegnierungs G. in.

b- He, Leip many Germany, a corporation of Ger- Application September28, 1934, Serial No.

13 Claims.

substance into the wood, it has hithertobeen.

considered necessary to cut the trees while the sap content is at theminimum, that is, during the winter. The cut treesare dried for a longperiod of time during which the wood frequently becomes impregnated withspores of fungi, molds and other organisms. The impregnation is thencarried out with the aid of vacuum, pressure and elevated temperaturenecessitating the use of "complicated and expensive apparatus includingvacuum chambers or immersion tanks and means fcr heating the same.However, even with the expenditure of much time and expensive equipment,it has not been possible heretofore to extend the impregnation intotheheart wood of the tree.

It is a general object of the invention to effect the impregnation ofgreen wood by a simple and economical process which makes use of thenatural phenomenon of osmosis to bring about the substantially completeimpregnation of the wood without the use of vacuum, pressure or elevatedtemperature. 3

It is another object of the invention to preserve green wood byimpregnating wood substantially completely with a preservative andfixing the preservative so as to prevent its escape when the wood issubjected to leaching soil.. It is a further object of the invention topreserve green wood by applying to the surface of the wood apreservative carried in a medium which enables the preservative todifiuse into the wood by osmosis and retarding the drying out of thetreated wood until the preservative has so diffused into the wood.

It is a specific object of the invention to provide a novel process forthe preservation of green wood characterized by the use ofa'preservative adapted to penetrate the wood by osmosis, a pro tectiveagent adapted to penetrate the wood by capillary diffusion and toprevent the escape of the preservative'from the-wood, and a carrieradapted to bring the preservative and" protective agents into intimatecontact with. the surface of wood.

by rain or damp' of treatment.

In Germany January 19, 1931 Other objects of the invention will in partbe obvious and will in part appearhereinafter.

The invention accordingly comprises a process having the steps and therelation of steps, one toanother, and a composition having theingredientsarfi" the proportion of ingredients all as set forth in thefollowing detailed description and the-scope of the application of whichwill be given in the claims.

For a more complete understanding of the nature and objects of theinvention, reference should be had to the follbtving detaileddescription taken in connection with the accompanying drawing, in which;

Fig. 1 illustrates a method of debarking felled the timber in accordancewith the process of invention;

' Fig. 2 illustrates a method of applying the impregnating substance tothe debarked trees;

Fig. 3 illustrates one 0d of stacking the treated trees in accordancewith the invention;

Fig. 4 illustrates one embodiment of the method of protecting thetreated and stacked trees from atmospheric conditions; and

' Fig. 5 is a view in section pregnated in invention.

According to the invention, the preservation of green wood is carriedout by stripping the bark 0 from green trees immediately after they havebeen cut down, coating the debarked surface with a paste comprising apreservative adapted to impregnate the wood by osmosis, a pasteformingcolloidal substance, water, and preferably a protective agent adapted toimpregnate the wood by capillary diffusion and to prevent tli'e..1escapeof the preservative, and protecting the coated wood from excessivedrying out until the preservative has diffused substantially into 40wood.

, The process of the invention is carried out preferably in the forestwhere the trees are felled, but it may be carried out at a concentrationcamp or treating place, in which case the trees are not debarked untilthey reach the place As shown in Fig. 1, a freshly cut I green tree I iscut down and trimmed as desired. The bark 2 is removed from the tree bya suitable means and then, without barked surface to dry out to asubstantial degree, a coating 3 of the .paste is applied by suitablemeans such, for example, as a brush 4 as shown I in Fig. 2 or a sprayingdevice. The amount of paste applied is varied in accordance with the Iembodiment of the meth- 20-" 25 4 of a tree trunk imaccordance with theprocess of the permitting the de- :For the most efiective .from thewind,

.The coated wood is then stacked and the drying out retarded atatmospheric temperatures until the impregnation is substantiallycomplete.

It has been found that the degree of impregnation is a function of themanner in which the treated wood is stored during the drying period.

stacked as close together as possible. For example, as shown in Fig. 3,the treetrunks I are arranged parallel in a three-cornered stack 4 withtheir arcuate surfaces contacting each other as they lie side by side,as illustrated in Fig. 4. When the tree trunks vary in length, thetrunks of the same length are stacked together with the longer trimksforming the bottom layers and 4 upper layers. The stack isv thenenclosed in a waterproof and windproof covering 5. This covering maycomprise a layer of straw 6r, as shownbe fashioned of strips clothpositioned in Fig. 4. the covering may 6 of tar-impregnated paper orlengthwise of the stack with the lower edges of.

each strip overlapping the upper edge of the next strip, as in layingshingles. The strips may be fastened together and held against the woodby known means such, for example. as tacks I driven through the overlapsdirectly into the underlying. wood. The covered in order that a windblowing lengthwise of the stack may not pass through the intersticesbetween the tree trunks and'dry out the surface of the wood. The bottomof the stack may be protected by a covering in a like manner. The entirestack may be supported abovethe ground by suitable sleepers positionedtransverse of the stack as shown in Fig. 4.

changes but-seldom, so that the drying out of the wood is retarded andthe natural moisture of the wood remains until the impregnation issubstantially complete. Enclosing the coated wood in a protectivecovering as described has been found to inhibit materially the checking"of the wood, that is, the development of cracks in the wood.

As an alternative to the above .described covering, each of theindividual tree trunks may be enclosed in a protective bandage orcovering. For example, the paste may be applied to a strip of paperhaving a width of from 10 to 15 cm. and the strip wound spirally aboutthe debarked tree trunk, the turns of the strip overlapping so as tocompletely cover the surface.

As long as moisture remains in the wood, the impregnation proceeds.Therefore, the protective covering is left on the wood to retard thedrying for'a period suificient to effect the desired impregnation, whichperiod is usually from two to four months. Obviously, when. theimpregnation is completed, the covering 'may be removed and the woodpermitted to dry as desired.

The composition utilized in the process of the invention consists of anypreferably one comprising a preservative agent adapted to penetrate thewood by osmosis, a paste-forming colloidal substance and water, andpreferably also a protective agent adapted to penetrate the wood bycapillary diffusion.

For the preservative agent, there is employed impregnation, the wood isthe shorter trunksiorming the end of the stack'also. is

the air within the intersticessuitable aqueous paste coppersulphate,'potassium sulphide, mercuric chloride,'zinc fiuorosilicate. Ifdesired, the preservative may comprise one or more insecticides such,for example, as a soluble arsenic salt such as sodium orpotassiumarsenite, sodium or potassium arsenate. The water-solublesubstances may be employed either singly or in admixture. The inorganicsubstance should be preferably one with high solubility in water andhigh mobility, that is, high osmotic pressure and rate of diffusion. 1

Further, the invention contemplates the use of pastes comprising two ormore soluble inorganic substances capable of reacting to form within thewood an insoluble or difficultly soluble product.

For example, with a fluoride or an arsenate, there may be used awater-soluble, inorganic dichromate such as sodium or potassiumdichromate. It would appear that the dichromate salt is reduced, withinthe wood, to a chromate salt which reacts with the fluoride or' arsenateto form a diflicultly soluble product having the general structure of acryolite compound.

For the protective agent, there is employed an organic substance such,for example, as dinitrophenol, dinitrocresol, tar oils, liquidpetroleum. The protective agent is preferably one'which is substantiallyinsoluble in water or incompletely miscible therewith, and which has alow viscosity and a high toxicity toward fungi, insects. The expressionwater-insoluble organic .substance shall include organic substanceshaving a relatively slight solubility in water'when compared tothe-water-soluble preservative agentsherein disclosed. v I

' The paste-forming ingredientcomprises preferahly a gultinous substancecapable of forming a water-swelling colloid such,- for example, as

starch, disintegrated casein, glue, gelatine, agar agar, gum arabic;This ingredient is prefer-- ably one adapted to give a tacky paste withwater. In general, the preservative agent comprises from. about 50% tothe protective agent from about 10%. to 35% and the glutinous substancefrom about 5% to 20% by weight.

By way of illustration, but not by way of limit-- ing the scope of theinvention, the following examples are given, the ingredients being inparts by weight.

Examples I n m IV v v1 Sodium fluoride 000 900 900 Sodium "senate 50.150

Dinitrophenol 170 170 170 50 36 70 Gum arabic. 30

Disintegr ted casein 10 firm-oh 80 40 -The several ingredients areground and mixed thoroughly with water in an amount sufilcient to'give apaste of the required viscosity.

If desired, the paste may comprise'a wetting agent such, for example, asglycerine, to assist in bringing the preservative and the protectiveagent into more intimate contact with the wood. -There may be addedalso, if desired, substances adapted to color the wood or to render thesame fireproof, mothproof, etc.

If desired, the protective agent may be applied to the wood byincorporating it in the paste water-soluble, inorganic and/or byapplying it alone as a coating subsequent to the application of thepaste to the wood. For example, the debarked wood may be coated firstwith an aqueous paste comprising a preservative, a paste-formingglutinous substance and water, and a protective agent of the classdescribed is subsequently applied to the wood, by

coating or otherwise, after the paste has dried and before and/or afterthe wood has become air dry.

There is illustrated in Fig. 5 the cross section' of a tree trunktreated according to the process of the invention. The preservativeagent being a salt, diffuses by osmosis through the cell walls into thewood cells; it also diffuses through the capillaries and intersticesbetween the cells. The penetration of the salt is rapid. and to asubstantial depth as indicated by the area designated A.-- In time thesalt may difattack. It the green protective agent ,preservative when thein damp soil or exposed to rain.

tinuously decreases as in the wood which fuse completely throughout theheart wood I as well as throughout the sap wood 9.

The protective agent, being an organic substance and insoluble in water,diffuses chiefly through the capillaries and the interstices be tweenthe cells. The depth of penetration is slight compared to that of thewater-soluble preservative, the ratio of the depths of penetra-- tionbeing about 1: 4, and the penetration of the is confined to theoutermost. layers as shown by the area designated B. This area B,impregnated by the water-insoluble organic substance, forms a waterproofzone which prevents the leaching out of the water-soluble treated timberis placed The paste-forming substance dries on the surface of the woodto form a hornycoating'designated C which prevents the paste from beingwashed'o'fi or falling off during the storing period. If there arecracks In in the tree trunk, the paste fills the same and at thesepoints the inwardly diffusion is more or less increased, depending uponthe depth of the crack.

Since the area of wood to be impregnated conthe salt difluses inwardlytoward the center of the tree. the fall in the concentration of the saltis very gradual. The outer layers contain the impregnating agents in thehighest concentration, which is highly desirable since these" layers aremost subjectto tree is cut down whenthe Sap is at the maximum, and thefreshly cut tree treated with the composition of the present invention,it frequently happens that the osmotic diffusion of thewater-solublesalt proceeds to completion even after the outer layers ofthe tree have become air dry.

The process of the present invention is applicable for the preservationof various types of woods such, for example, as pine, fir, spruce,larch, beech, oak and ash. The process may be carried out on the entiretree trunk or upon finished or partly finished lumber or timbers cutfrom trees The process is especially applicable. for the treatment 01'telegraph poles, fence poles, structural timbers and other woods used inthe open. Trees intended for'use as mine timber, cross ties and marinepiles are preferably treated with the compositions containing fluorideanother pair of inorganic salts an insoluble compound withis resistantto leaching when the wood is immersed in water or damp soil.

, By the present invention there has been proand dichromate-or capableof forming trate the wood by treated before the vided a novel pree'ssfor preserving green wood having many new and unusual advantages. Theprocess permits the tree to be cut down while the sap is at the maximum,i. e. in the spring and summer when the cutting operations are.unencumbered by snow and ice. The tree may be wood has been attacked byinsects and plant organisms. Any cracks existing in the surface of thewood are filled with the paste, in consequence of which the impregnationis deeper at these points and the protection at a maximum. The coatingof aqueous paste and the action of the impregnating salt on the sapslows up the rying of the wood and retards the development of injuriouscracks in the wood.

Further, the present process is characterized by its simplicity andeconomy of operation and equipment, despite which the depth ofpenetration is greater than that obtained by the use of vacuum, highpressure and elevated temperatures.

The presentinvention shortens the useless life of cut timber because theimpregnation and drying out proceed simultaneously instead ofsuccessively as in the usual practice.

Since certain changes in carryingv out the above process, and certainmodifications in the composition which embody the invention may be madewithout departing from its scope, it is intended that all mattercontained in the above description shall be interpreted as illustrativeand not -in a limiting sense.

In the appended claims, the expression green woodfis intended 'todesignate both green wood containing live sap and wood which isrelatively preservative has diffused substantially into the wood.

2. In a process for preserving green wood, the steps comprising coatingdebarked wood on its outer surface with an aqueous tacky pastecomprising a water-soluble preservative, a pasteforming colloidalsubstance and water, and retarding the drying out the preservative hasdiffused substantially into the wood.

3. In a process for preserving green wood, the

steps comprising debarking freshly cut trees, coatingthe debarkedsurface with an aqueous paste comprising a preservative adaptedtopenetrate the wood by osmosis, a protective agent adapted to penetratethe wood by capillary diffusion, a paste-forming colloidal substance andwater, and retarding the wood until the preservative has diffusedsubstantially into the wood.

4. In a process for preserving green wood, the steps comprisingdebarking freshly cut trees, coating the debarked surface with anaqueous paste comprising a preservative adapted to peneosmosis, aprotective agent adapted to penetrate the wood by capillary difdryingout of the coatedof the coated wood until 1 outer surface whereby dryingout fusion, 9. paste-forming colloidal substance and water, arrangingthe coated wood in a closely packed stack, enclosing the stack in awaterproof and windproof covering and maintaining the stack in a coveredcondition until the preservative has diifused substantially into thewood.

5. In a process for preserving green wood, the

steps comprisingdebarking freshly cut trees and coating the debarkedsurface with an aqueous paste comprising a water-soluble inorganicsubstance, a paste-forming colloidal substance and water, and thereafterapplying to the debarked surface a water-insoluble organic substanceafter the paste has dried.

6. In a process for-preserving green wood, the steps comprisingdebarking freshly cut trees, coating the debarked surface with anaqueous paste comprising a water-soluble inorganic substance, awater-insoluble organic substance, 9. paste-forming colloidal substanceand water, the inorganic substance penetrat'ng the woodby osmosis to asubstantial. depth and'the organic substance forming in the outermostlayers of the wood a waterproof zone substantially preventing theleaching out of the inorganic substance, and enclosing the coated woodin a protective covering.

7. In a process for preserving green wood, the steps comprisingdebarking coating the debarked surface with an aqueous paste comprisinga water-soluble inorganic fluoride, a water-soluble inorganicdichromate, dinitrophenol, a paste-forming colloidal substance andwater, the fluoride and the dichromate A reacting within the wood toproduce a waterinsoiuble product.

8. In a process green wood, the wood on its outer surface with anaqueous tacky paste comprising a water-soluble preservative, apasteforming colloidal substance and water, and enclosing the coatedwood in a protective covering of the coated wood is retarded untilithepreservative has diffused subfor preserving stantially into the wood.

9. In a process for preserving green wood, the

steps comprising coating debarked' wood on its prising a preservativeadapted to penetrate the wood by osmosis, a paste-forming colloidal sumtive has diffused substantially freshly cut trees,

with an aqueous tacky paste comstance and water, arranging the coatedwood in a. closely packed stack, andenclosing the stack in a protectivecovering whereby the drying out of the coated wood is retarded until thepreservainto the wood. 10. In a process for preserving green wood, thesteps comprising coating debarked wood on its outer surface with anaqueous tacky paste com-, prising a preservative adapted to penetratethel wood by osmosis, a paste-forming colloidal substance and water,retarding the drying out of the coated wood until the preservative hasdiffused substantially into the wood and thereafter applying to thesurface of the wood a. water-insoluble organic substance, said organicsubstance 15 forming in the outermost layers of the wood a waterproofzone substantially preventing the leaching out of the preservative.

1-1. In a process for preserving green wood, the steps comprisingcoating debarked wood onits outer surface with an aqueous tacky pastecomprising a water-soluble preservative in an amount of from 50% to 80%,a water-insoluble protective agent in an amount of from about 10% to35%, a paste-forming glutinous substance in an amount of from about 5%to 20% by weight, and water, and retarding the drying out of the coatedwood until the preservative has diffused substantially into the wood.

12. In a process for preserving green wood, the steps comprising coatingdebarked wood on its outer surface with an aqueous tacky pastecomprising a water-soluble inorganic dichromate, a water-solubleinorganic fluoride, a paste forming colloidal substance and water, thedichromate and the fluoride forming within the wood a waterinsolubleproduct, and retarding the drying out of the coated wood until thepreservative has dlfiused substantially intothe wood.

13. Inga process for preserving green wood, the steps comprising coatingdebarked wood on its outer; surface with an aqueous tacky pastecomprising a water-soluble inorganic dichromate, a water-solubleinorganic arsenate, a paste forming colloidal substance and water, thedichromate and the arsenate forming within the wood a water-insolubleproduct, and retarding the drying out of the coated wood until thepreservative has diffused substantally into the wood.

CARL SC

